The ability to run fast is an important asset in most all sports. Therefore, athletes and their coaches have developed various exercises and apparatus that are intended to improve this ability.
There are numerous characteristic of sprinting that determine one's ability to sprint fast. The act of sprinting involves the runner swinging his legs to perform a scissors motion which is accomplished by vaulting himself off the ground alternately using each foot. Characteristics that are obvious to the observer in determining speed of running are frequency of stride and stride length. Properties of the musculature that are relied upon to attain large frequency and stride length are strength and quick neurological reflexes in the hip flexors and extensors. Consequently, considerable emphasis has been placed on developing apparatus and exercise designed to strengthen and quicken the hip flexors and extensors.
For example, U.S. Pat. No. 4,456,248 to R. S. Smith is for a rack type of apparatus on which the athlete can perform situps and back extensions.
Another exercise is performed with a rope and pulley arrangement wherein one end of the rope is attached to the athlete, the rope passes through a pulley attached to his partner and the other end is fixed. The partner is positioned ahead of and attempts to run away from the athlete. Because of the pulley, the athlete must run twice as fast as the partner. Consequently, he becomes accustomed to running at top speed and thereby develops his neurological responses.
U.S. Pat. No. 4,728,100 to R. S. Smith is for a device incorporating a photocell in which the user interrups a light beam to time his repetitions in order to increase frequency of his movements.
Exercises intended to improve the runner's ability to vault himself off the ground involve the athlete's jumping off a platform and landing on his feet (referred to as "pliometrics"). The shock of the landing has been found to strengthen the muscles (ankle and knee extensors) involved in jumping.
Less attention has been directed toward the runners ability to vault himself off the ground. The lack of attention to this characteristic is undoubtedly due to the fact that a top sprinter vaults himself vertically only about two inches off the ground with each stride so that this characteristic does not appear to be important to the casual observer. However, calculations performed by the author show that the grounded foot must exert a force on the ground of about six times the body weight for about 30 milliseconds in order to vault the athlete two inches into the air when his stride frequency is about five strides per second. The weaker the athlete from the standpoint of the vertical force that he can exert, then the longer will be the time required to exert the force (referred to hereinafter as contact time.). Therefore, even though he may have superior hip flexors and extensors, his excessive contact time would reduce his stride frequency and thereby prevent him from making full use of his potential hip flexing ability.
In order to reduce the time of foot contact and correspondingly increase the athlete's applied vertical force during foot contact, the exertion must come from the ankle extensors rather than the knee extensors. In other words, the knee should not "sag".
In the following description of the invention, embodiments are presented which include novel combinations of circuits that have been described in the prior art. These descriptions may be found in application notes published by manufacturers of integrated circuit components. In particular, the following circuits are described in a book entitled "CMOS COOKBOOK" by Don Lancaster published by Howard W. Sams and Co., 4300 62nd St. Indianapolis, Ind. 46268. The table includes the component title, its manufacturer identification number and the page in the CMOS COOKBOOK where the component is discussed and has particular relevance to the embodiments of this invention:
______________________________________ 4001 Crystal Oscillator page 237 4026 Single Package per Decade Counting page 308 System 4013 Dual D Flip Flop page 74 4528 Monostable Multivibrator page 250 4050 Debounce Switch page 221 NPN transistor Darligton Transistor Drive page 46 4001 Hold Follow Latch page 217 ______________________________________
An additional reference is U.S. Pat. No. 4,745,259 to Russ et al which describes the setting of thumbwheel switches in conjunction with counter chips LS240 to establish a predetermined count representing a desired length of weld to be compared to a measured count representing an actual length of weld using comparator IC's LS682.